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What is Ecology?
 The study of living things in relation to each
other and to their environment.
An Introduction to Ecology
 Common Terms Used in Ecology:
– Habitat
– Population
– Community
– Ecosystem
Source from: Environmental Science: Working
With the Earth. (6th ed.)
The Ecosystem
 A self-regulating community of plants and
animals interacting with one another and
with their non-living environment.
 An ecosystem contains two basic
components:
– Physical factors
– Biotic factors
The Ecosystem
 These two factors affects the number, types,
distribution, behaviour, and adaptation
shown by organisms.
Source from: Environmental Science: Working with the Earth. (6th ed.)
Physical Factors
 Physical factors:
– Temperature
– Light
– Wind
– Water
– Soil
Biotic Factors
 Refer to all organisms in an ecosystem.
They may interact with each other in more
than one way.
 Living organisms can be divided into three
main classes:
– Producers
– Consumers
– Decomposers
Energy flow within an ecosystem
 Food Chain
– Producers ----> Primary Consumers ---->
Secondary Consumers -----> Tertiary
Consumers
– It represents the sequence in which food
materials are transferred from one organism to
another.
Energy flow within an ecosystem
Source from: Environmental Science: Working with the Earth. (6th ed.)
Energy flow within an ecosystem
Source from: Environmental Science: Working the Earth. (6th ed.)
Energy flow within an Ecosystem
 Roles of Producers, Consumers and
Decomposers in Relation to Energy flow.
– Producers
• absorb light energy and convert them to chemical
energy to be stored
– Consumers
• feed on producers and one another, then energy
transferred.
Energy flow within an Ecosystem
– Decomposers
• When break down their food, and energy locked in
the dead bodies, faeces and excretory products is
released and lost from the ecosystem.
Energy flow within an Ecosystem
 Food Webs
– Food chains appear in interconnected forms
which are called food webs.
Energy flow within an Ecosystem
Source from: Environmental Science: Working the Earth. (6th ed.)
Energy flow within an Ecosystem
 Trophic Levels
– The position that an organism occupies in a
food chain is called its tropic level.
Source from: Environmental Science: Working the Earth. (6th ed.)
Energy flow within an Ecosystem
 Energy Transfer between Trophic Levels
Source from: Environmental Science: Working the Earth. (6th ed.)
Energy flow within an Ecosystem
 Only 10% of energy used by the organism.
Energy lost:
– as heat during respiration
– in activities,
– through excretion, egestion and death.
 Food chain rarely includes more than five
trophic level.
 Energy cannot be recycled and re-used.
Energy flow within an Ecosystem
 Ecological pyramids.
Source from: Environmental Science: Working the Earth. (6th ed.)
Energy flow within an Ecosystem
 Pyramid of energy
– The energy available for growth decreases
along a food chain.
 Pyramid of numbers
– The drop in numbers of organisms at each
trophic level
 Pyramid of biomass
– Biomass is the total mass of organisms in a
trophic level.
Energy flow within an Ecosystem
Source from: Environmental Science: Working the Earth. (6th ed.)
Cycling of Materials in
Ecosystems
 Carbon Cycle
Source from: Environmental Science: Working the Earth. (6th ed.)
Cycling of Materials in
Ecosystems
 Nitrogen Cycle
Source from: Environmental Science: Working the Earth. (6th ed.)
Ecological Interdependence of
Organisms
 In an ecosystem, organisms may interact
with each other in many different ways:
–
–
–
–
–
Predation
Competition
Mutualism
Commensalism
Parasitism
Ecological Interdependence of
Organisms
 For each type of interrelationship, the organisms concerned may be
benefited (+), harmed (-), or not affected (0)
Type if interrelationship
Predation
Competition
Mutualism
Commensalism
Parasitism
Organism 1
Predator +
+
Commensal +
Parasite
+
Organism 2
Prey
+
Host
0
Host
-
Man and Micro-organisms
Micro-organisms
 Micro-organisms are very small organisms
that can be only seen by a microscope.
 There are 5 major types of micro-organisms:
 Bacteria
 virus
 fungi
 protozoa
 algae
Useful Micro-organisms
 Wine and Bread Making:
Anaerobic bacteria + Sugar --> Alcohol + CO2
 Bacteria and Fungi as Decomposers
 Symbiotic Bacteria in Leguminous Plants
 Bacteria and Fungi in Sewage Disposal
 Antibiotics
Harmful Micro-organisms
 Causing Diseases.
 Spoilage of Food and Useful Materials
Food Preservation
 Food is preservation so that they can be
transported long distance and stored for
long periods.
 Food preservation is designed to kill the
micro-organisms and/or slow down their
growth rate.
Common Food Preservation
Methods
 Heating
 Canning and bottling
 Pasteurization
 Refrigeration
 Freezing
 Drying (Dehydration)
 Smoking
Common Food Preservatives
Methods
 Pickling
 Osmotic preservation
 Ultra high temperature
(UHT) treatment
 Adding preservatives
Pickling food.
Source from: Biology: A Modern Approach 2. (2nd ed.)
Man’s Effect on His Environment
Land Use
 Monoculture means remove diversity of
species of plant from a place and replace it
with a dense single species year after year.
 Deforestation is uncontrolled cutting down
or burning of trees.
Effects of Deforestation
Source from: Environmental Science: Working the Earth. (6th ed.)
Pollution
 Pollution is the introducing of substance to
air, water, soil, or food that threatens the
health, survival, or activities of human or
other living organisms.
 Pollutants is the chemical or forms of
energy that can causes pollution.
Air pollution
 Pollution of atmosphere.
 Causing by burning fossil fuels in power
plants, factories and vehicle engines.
Vehicle engines produce air pollutants such as CO, lead, and dust
particles.
Major Air Pollutants
 Carbon Monoxide.
 Carbon Dioxide.
 Sulphur Dioxide and Nitrous Oxides.
 Carbon and Dust Particles.
 Lead
 Radioactivity.
Formation of Smog
In normal condition, the
warm and polluted air
can be dispersed into
high attitudes.
When temperature
inversions occurs, the cool
air is trapped by the warm
air above, so the polluted
air cannot be dispersed and
remains in the city.
Source from: Environmental Science: Working the Earth. (6th ed.)
Water Pollution
 Pollution of water bodies such as steams,
lakes and seas.
 Caused by discharge of domestic, industrial
and agricultural wastes to the water bodies.
Acid Rain Formation
Source from: United States Environmental Protection Agency.
Major Types of Water Pollution
 Chemical pollution.
 Sewage and Manure.
 Detergents and Inorganic Fertilizers.
 Oil Pollution.
 Thermal Pollution.
How Red Tides Kill Aquatic
Organisms?
 Rich nutrients in pollutants leading to algal
bloom.
 The dead bodies of algae provide nutrients
for the growth of saprophytic bacteria,
leading rapid increase of tits population.
 The bacteria kills the aquatic organisms in
three ways:
 Use up the oxygen in water.
 Accumulate in gills of organisms.
 Excrete toxins which may kills the
organisms.
Noise Pollution
 Noise is any unpleasant sound in the
environment.
 Common noise is come busy traffic, piling,
aircraft, or playing mah-jong in midnigh,etc.
 The degree of loudness is measured in
decibels. (db)
 Noise above 60db is harmful to human.
Conservation
 Conservation is the management of
environment in a planned and sustainable
way so that the environment is least
disturbed and able to yield the best benefits
to mankind.
Source from: Environmental Science: Working the Earth. (6th ed.)
Needs of Conservation
 To meet the needs of ever increasing human
population, mankind exploited environment
in insensible ways.
 These activities deplete the environment
and deprived the natural , leading the Earth
become unsuitable for all forms of life,
including the human himself.
 Conservation must be taken to save the
ecosystem and human himself.
The Principle of Conservation
 Recycling of Used
Materials.
 Pollution Control.
 Conservation of Wild
Life.
Africa elephants were killed
their tooth to make ivory goods.
Legislation of abandon trading
of ivory goods was established
in 1989.
Source from: Environmental Science: Working the
Earth. (6th ed.)
Sewage Treatment
Source from: Water Supplies Department, HKSAR.